Field of the Invention. The present invention relates generally to the field of shutter mechanisms for collimating x-rays. More specifically, the present invention discloses a compact shutter mechanism allowing direct, independent control of two orthogonal sets of shutters.
Shutter mechanisms for x-ray collimators involve a unique set of design requirements. The shutters are typically made of a radio-opaque material, such as lead. This results in shutters that have substantial weight if they are large. In addition, x-ray diagnostic devices used in medical and dental offices are subject to very tight space limitations. Therefore, the shutter mechanism should be compact as possible to meet these space and weight constraints.
In addition, the safety of the patient and healthcare providers is always of paramount concern. This dictates that the shutter mechanism must be capable of a high degree of positional accuracy to ensure an accurate x-ray dosage to the patient through a well-defined aperture, and to prevent accidental exposure of others.
The prior art in the field of shutter mechanisms for collimating x-rays includes the applicant's U.S. Pat. No. 5,396,534 (Thomas). A flexible band extends in sliding engagement about the periphery of an opening in a frame. FIG. 9 of this patent shows an embodiment using two orthogonal pairs of shutters to create an aperture that is adjustable in two dimensions.